How to Migrate PL/SQL Code from Oracle to PostgreSQL

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Stored procedures and functions are crucial components of databases used to encapsulate the logic of data flow. In Oracle, stored procedures are commonly used for this purpose, while in PostgreSQL, functions are the preferred choice. However, migrating stored procedures, functions, and triggers from Oracle to PostgreSQL is a complex task that requires careful consideration and planning. This article explores some tips and tricks to help database engineers or other responsible staff migrate source code from Oracle to PostgreSQL.

When migrating from Oracle to PostgreSQL, it is important to note that Oracle uses packages to organize functions into semantic groups, whereas PostgreSQL uses schemas for the same purpose. Additionally, there are no package-level variables in PostgreSQL, but they can be emulated as data of a temporary service table. To ensure a successful migration, it is important to research best practices for translating stored procedures from Oracle to PostgreSQL functions to understand both systems and the problem that the respective procedure/function solves, instead of simply converting the syntax.

It is also important to note that there is a difference in how variables are declared in Oracle stored procedures and PostgreSQL functions. In Oracle, variables can be declared anywhere, while in PostgreSQL, local variables must be declared at the beginning of the function. This syntax difference requires a change in habit, and careful attention must be paid to ensure that the new function operates correctly.

In addition to syntax differences, it is important to have a good understanding of both Oracle and PostgreSQL before beginning the migration process. If your application uses proprietary features of Oracle, you will need to rewrite those parts of the application that use Oracle. It is essential to address any differences in syntax and functionality between the two systems to ensure a smooth transition.

To make the migration process easier, it is possible to use special tools that can partially automate the migration of stored procedures, functions, triggers, and views from Oracle to PostgreSQL. One such tool is the Oracle to PostgreSQL Code Converter developed by Intelligent Converters. This tool can migrate stored procedures, functions, triggers, and views, and convert Oracle built-in functions into PostgreSQL equivalents. Predefined Oracle types are mapped into PostgreSQL, and reserved words and identifiers are handled intelligently. Source code can be extracted directly from the database or from a PL/SQL script file.

Although the Oracle to PostgreSQL Code Converter automates the migration of basic syntax patterns and constructions, some manual post-processing of the output code may be required, especially for large and complicated fragments of the source code. Therefore, it is essential to test the migrated code thoroughly to ensure that it operates correctly.

In conclusion, migrating stored procedures, functions, and triggers from Oracle to PostgreSQL is a complex task that requires careful planning and execution. It is important to research best practices for translating stored procedures from Oracle to PostgreSQL functions and to understand the differences in syntax and functionality between the two systems. Additionally, it may be helpful to use special tools such as the Oracle to PostgreSQL Code Converter to partially automate the migration process.